首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   114篇
  免费   2篇
系统科学   3篇
现状及发展   49篇
研究方法   19篇
综合类   44篇
自然研究   1篇
  2020年   1篇
  2018年   3篇
  2017年   4篇
  2016年   2篇
  2013年   1篇
  2012年   7篇
  2011年   8篇
  2010年   1篇
  2008年   5篇
  2007年   5篇
  2006年   4篇
  2005年   9篇
  2004年   3篇
  2003年   7篇
  2002年   3篇
  2001年   2篇
  2000年   3篇
  1999年   3篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1986年   2篇
  1985年   1篇
  1981年   1篇
  1980年   3篇
  1979年   7篇
  1978年   2篇
  1977年   1篇
  1976年   5篇
  1975年   4篇
  1974年   2篇
  1972年   2篇
  1969年   1篇
  1968年   2篇
  1966年   3篇
  1965年   2篇
  1955年   1篇
  1954年   1篇
  1946年   1篇
排序方式: 共有116条查询结果,搜索用时 15 毫秒
91.
The Clara cell 16 kDa protein (CC16) maps to an atopy-associated region of chromosome 11 and has been ascribed an anti-inflammatory function. Using reverse-phase HPLC and Western blot analysis, we have evaluated the polypeptide pattern in bronchoalveolar lavage (BAL) fluid retrieved from asthmatics, before and after induction of airway inflammation by low-dose allergen inhalation challenge. A prominent decrease of CC16 was seen after induction of inflammation, and a further CC16 decrease was observed in lavage fluid where surfactant had been removed. Reduced levels of pulmonary CC16 may cause loss of anti-inflammatory activity in the airways and contribute to the development of airway inflammation in asthma. Received 22 March 2000; received after revision 4 May 2000; accepted 4 May 2000  相似文献   
92.
93.
94.
Cross‐institutional forecast evaluations may be severely distorted by the fact that forecasts are made at different points in time and therefore with different amounts of information. This paper proposes a method to account for these differences when analyzing an unbalanced panel of forecasts. The method computes the timing effect and the forecaster's ability simultaneously. Monte Carlo simulation demonstrates that evaluations that do not adjust for the differences in information content may be misleading. In addition, the method is applied to a real‐world dataset of 10 Swedish forecasters for the period 1999–2015. The results show that the ranking of the forecasters is affected by the proposed adjustment.  相似文献   
95.
Many hemiepiphytic plants secrete a thick layer of mucilage to limit desiccation and protect against fungal pathogens. With its stable moisture and protected location, this mucilage constitutes a potentially attractive microhabitat for small animals; however, until now, no animal species have been recorded from it. Larvae of a psychodid fly were collected from the mucilage of a hemiepiphytic Araceae in Braulio Carillo National Park, Costa Rica. Rearing of the larvae yielded specimens of pupae and one adult male described here as Mucomyia emersa Kvifte and Curler gen. nov. sp. nov. An additional species from Costa Rica, Mucomyia browni Kvifte sp. nov., is described based on adult males from the Zurquí de Moravia forest reserve. Mucomyia belongs to tribe Psychodini, which comprises both habitat generalists and specialists. The new species are morphologically similar to those in Philosepedon s. str. and Eurygarka, both of which are known to develop in snail carrion. It is premature to speculate about whether or not species in the new genus are restricted to hemiepiphyte mucilage.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:37CD136B-53D8-4D3E-A34A-3BE4859045E5  相似文献   

96.
97.
Mutations generate sequence diversity and provide a substrate for selection. The rate of de novo mutations is therefore of major importance to evolution. Here we conduct a study of genome-wide mutation rates by sequencing the entire genomes of 78 Icelandic parent-offspring trios at high coverage. We show that in our samples, with an average father's age of 29.7, the average de novo mutation rate is 1.20?×?10(-8) per nucleotide per generation. Most notably, the diversity in mutation rate of single nucleotide polymorphisms is dominated by the age of the father at conception of the child. The effect is an increase of about two mutations per year. An exponential model estimates paternal mutations doubling every 16.5?years. After accounting for random Poisson variation, father's age is estimated to explain nearly all of the remaining variation in the de novo mutation counts. These observations shed light on the importance of the father's age on the risk of diseases such as schizophrenia and autism.  相似文献   
98.
The inflammasome regulates the release of caspase activation-dependent cytokines, including interleukin (IL)-1β, IL-18 and high-mobility group box 1 (HMGB1). By studying HMGB1 release mechanisms, here we identify a role for double-stranded RNA-dependent protein kinase (PKR, also known as EIF2AK2) in inflammasome activation. Exposure of macrophages to inflammasome agonists induced PKR autophosphorylation. PKR inactivation by genetic deletion or pharmacological inhibition severely impaired inflammasome activation in response to double-stranded RNA, ATP, monosodium urate, adjuvant aluminium, rotenone, live Escherichia coli, anthrax lethal toxin, DNA transfection and Salmonella typhimurium infection. PKR deficiency significantly inhibited the secretion of IL-1β, IL-18 and HMGB1 in E. coli-induced peritonitis. PKR physically interacts with several inflammasome components, including NOD-like receptor (NLR) family pyrin domain-containing 3 (NLRP3), NLRP1, NLR family CARD domain-containing protein 4 (NLRC4), absent in melanoma 2 (AIM2), and broadly regulates inflammasome activation. PKR autophosphorylation in a cell-free system with recombinant NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC, also known as PYCARD) and pro-caspase-1 reconstitutes inflammasome activity. These results show a crucial role for PKR in inflammasome activation, and indicate that it should be possible to pharmacologically target this molecule to treat inflammation.  相似文献   
99.
100.
In this paper we present a case of a structured, facilitated group process with a climate action group engaged in a local Transition initiative. We explore how the interacting contexts between action researchers and the group acted as a constraint for the trajectory of the group process, by looking at the mismatches between the group’s and the researchers’ purposes and differences in expectations about methods of engagement. A methodological framework was used for evaluating the outcomes. The primary aim of this article was to investigate and point out dynamics that may be a hindrance to the effectiveness of a facilitated local climate initiative, with the view to inform facilitation practices and improve future action research processes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号